Removingbuild configuration

In code warrior 10.7 I have removed 2 build configurations by using 'Delete' in 'manage configuration'. But in the .cproject there still exist configurations for the removed configurations (e.g. <configuration configurationName="bin_6f"/>. Why isn't the build configurations removed from the .cproject-file? How could I remove the build configurations from .cproject-file? Of course I could remove the build configuration manually by using a text editor but that is not a preferred way.